text: ////////////////////////////////////////////////////////////////////////////////
  /// DISCLAIMER
  ///
  /// Copyright 2014-2020 ArangoDB GmbH, Cologne, Germany
  /// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
  ///
  /// Licensed under the Apache License, Version 2.0 (the "License");
  /// you may not use this file except in compliance with the License.
  /// You may obtain a copy of the License at
  ///
  ///     http://www.apache.org/licenses/LICENSE-2.0
  ///
  /// Unless required by applicable law or agreed to in writing, software
  /// distributed under the License is distributed on an "AS IS" BASIS,
  /// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  /// See the License for the specific language governing permissions and
  /// limitations under the License.
  ///
  /// Copyright holder is ArangoDB GmbH, Cologne, Germany
  ///
  /// @author Dr. Frank Celler
  ////////////////////////////////////////////////////////////////////////////////
  
  #ifndef ARANGODB_REST_SERVER_SERVER_ID_FEATURE_H
  #define ARANGODB_REST_SERVER_SERVER_ID_FEATURE_H 1
  
  #include "ApplicationFeatures/ApplicationFeature.h"
  #include "Basics/debugging.h"
  #include "ProgramOptions/ProgramOptions.h"
  #include "VocBase/Identifiers/ServerId.h"
  
  namespace arangodb {
  
  class ServerIdFeature final : public application_features::ApplicationFeature {
   public:
    explicit ServerIdFeature(application_features::ApplicationServer& server);
  
    void start() override final;
  
    static ServerId getId() {
      TRI_ASSERT(SERVERID.isSet());
      return SERVERID;
    }
  
    // fake the server id from the outside. used for testing only
    static void setId(ServerId serverId) { SERVERID = serverId; }
  
   private:
    /// @brief generates a new server id
    void generateId();
  
    /// @brief reads server id from file
    int readId();
  
    /// @brief writes server id to file
    int writeId();
  
    /// @brief read / create the server id on startup
    int determineId(bool checkVersion);
  
    std::string _idFilename;
  
    static ServerId SERVERID;
  };
  
  }  // namespace arangodb
  
  #endif